Aqueous mineral oil emulsions have long been known and used in formulating topical cosmetic and pharmaceutical compositions. Generally speaking, bioadhesiveness, i.e., the ability of a thick coating to adhere tenaciously to moist skin or a mucosal surface to which it is applied, is not a particularly important functional requirement. However, one end-use area in which bioadhesiveness is an important factor is in pharmaceutical compositions which are applied to wounds to promote the healing thereof. Oftentimes, the fluid exudate from the wound tends to create a barrier between the pharmaceutically active agent or agents in the pharmaceutical composition applied to the wound, especially to the exposed surface area of the wound. Alternatively, the fluid exudate will physically dislodge the pharmaceutical composition from the wound area, particularly when the wound is on the inside of the mouth, where copious amounts of saliva usually are present. In the case of a covered wound, the exudate can promote the absorption of the pharmaceutical composition into the wound covering and away from the surface of the wound.
In general, aqueous mineral oil emulsions have poor bioadhesiveness and the more viscous they are, the more likely they are to not form a bond to the surface of the wound, particularly when the wound is moist. This problem of non-adherence is particularly acute in the case of wounds, ulcers and lesions on the inside of the mouth. The saliva present in the mouth often prevents even initial adherence of the emulsion to the wound area or rapidly causes dislodgement of the emulsion from the wound area.
It has now been found that certain aqueous mineral oil emulsions can be rendered bioadhesive by a combination of a hydratable particulate hydroxypropyl methylcellulose and a water-dispersible polymer which inhibits the hydration of the hydroxypropyl methylcellulose prior to the application of the emulsions to a wound area. It has further been found that these novel aqueous mineral oil emulsions are excellent vehicles for woundhealing promoters, particularly for growth factors such as TGF.alpha..